Chieftec HPC-360-302 DF repair

During revive the retro computer I discovered a problem with a Chieftec power supply:

After powering it up it is emitting high frequency noise, mainboard is not starting after pushing the power button.

I connected the multimeter and measured the STB (standby) line (violet color in ATX connector) which has to be +5V. The result is around 500mV.

After searching on forums:

I’ve obtained information about similar problems and the schematic for this power supply:

It turn out that there is surely a problem with capacitors. I started with replacing two 3300uF/6.3V near the 3.3V line which was leaked (C13 and C15). Here are the new ones:

Next I replaced the main cause of the whole problem: 22uF/50V capacitor marked as C34. After removing, I measured the capacity and it was dropped to 18uF, which is sufficient to raise the problem. I replaced it with same capacity but 100V, and also a little higher in diameter so I have to raise it a little on the legs:

Soldering was a little problematic because it has a wire from another element in the same hole.

After all this I was trying to power it up but unfortunately nothing changed ๐Ÿ™
It was still generating this noise and standby line was not +5V.

After further investigation it turns out that there is a protecting 5.6V zener diode (D14) which is the last resort for protecting the main board. I’ve unsolder one leg to check the diode for sure:

… and indeed that was a problem ๐Ÿ™‚
I could also see a little overheat under that diode which was not visible before:

Finally I’ve replaced this zener diode with the other I have:

And finally after powering it up I can see +5V on standby line and no more noise!!! ๐Ÿ™‚

Power supply is working properly!

Here are all elements I’ve replaced:

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